<?php

//定义变量
$name = 'zhangsan';

//可变变量
$a = 10;
$b = 'a';
echo $$b; //10

//变量传递
//1.值传递
$num1 = 10;
$num2 = $num1;

//2.地址传递
$num3 = 10;
$num4 = &$num3;


//销毁变量
$num5 = 5;
unset($num5);
echo $num5; //Undefined variable








